HttpClient如何获取302响应中的Location跳转头信息及如何获取302跳转后的页面信息

向右看齐 2021-06-22 15:36 895阅读 0赞

http status 返回302的情况下，我们一般有如下两种需求

### GET方式： ###

1、获取302后的跳转链接URL，不获取URL对应的内容

public static String getLocationUrl(String url) {
    		RequestConfig config = RequestConfig.custom().setConnectTimeout(50000).setConnectionRequestTimeout(10000).setSocketTimeout(50000)
                    .setRedirectsEnabled(false).build();//不允许重定向   
    		CloseableHttpClient httpClient = HttpClients.custom().setDefaultRequestConfig(config).build(); 
    		String location = null;
    		int responseCode = 0;
     
    		HttpResponse response;
    		try {
    			response = httpClient.execute(new HttpGet(url));
    			responseCode = response.getStatusLine().getStatusCode();
    			if (responseCode == 302) {
    				Header locationHeader = response.getFirstHeader("Location");
    				location = locationHeader.getValue();
    			}
    		} catch (Exception e) {
    			
    			e.printStackTrace();
    		}
    		
    		return location;
    	}

2、直接获取302跳转后的页面内容（核心：setRedirectsEnabled(true)，默认也是true）

public static String getLocationUrl(String url) {
    		RequestConfig config = RequestConfig.custom().setConnectTimeout(50000).setConnectionRequestTimeout(10000).setSocketTimeout(50000)
                    .setRedirectsEnabled(true).build();//不允许重定向   
    		CloseableHttpClient httpClient = HttpClients.custom().setDefaultRequestConfig(config).build(); 
    		String location = null;
    		int responseCode = 0;
     
    		HttpResponse response;
    		try {
    			response = httpClient.execute(new HttpGet(url));
    			responseCode = response.getStatusLine().getStatusCode();
    			if (responseCode == 200) {
    				System.out.println(EntityUtils.toString(response.getEntity()));
    			}
    		} catch (Exception e) {
    			
    			e.printStackTrace();
    		}
    		
    		return location;
    	}

### POST方式：（form表单） ###

1、获取302后的跳转链接URL，不获取URL对应的内容

package thinking.in.spring.boot;
    
    import org.apache.commons.codec.binary.Base64;
    import org.apache.http.Header;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.CloseableHttpResponse;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.client.protocol.HttpClientContext;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClients;
    import org.apache.http.message.BasicNameValuePair;
    
    import javax.crypto.Cipher;
    import java.io.IOException;
    import java.net.URISyntaxException;
    import java.security.KeyFactory;
    import java.security.interfaces.RSAPublicKey;
    import java.security.spec.X509EncodedKeySpec;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    public class HttpClientUtils {
    
        public static void main(String[] args){
            String json = "{\n" +
                    "        \"Issuer_NAME\": \"car\",\n" +
                    "        \"EUID\": \"fccab33e-015e-11ea-95d9-000c292235b2\",\n" +
                    "        \"Campaign_ID\": \"1234567889\"\n" +
                    "}\n";
            CloseableHttpClient httpclient = HttpClients.createDefault();
            HttpClientContext context = HttpClientContext.create();
            HttpPost httpPost = new HttpPost("https://aaaaa.com");
            CloseableHttpResponse response = null;
            String location = null;
            try {
                Map<String,String> map = new HashMap<>();
                map.put("data", encrypt(json,"aaaaaaaa"));
                List<BasicNameValuePair> pair =new ArrayList<BasicNameValuePair>();
    
                //我们遍历map 将数据转化为我们的表单数据
                for (Map.Entry<String,String> entry:
                        map.entrySet()) {
                    pair.add(new BasicNameValuePair(entry.getKey(),entry.getValue()));
                }
    
                //httppost 中放入我们的经过url编码的表单参数
    
                httpPost.setEntity(new UrlEncodedFormEntity(pair));
                response = httpclient.execute(httpPost, context);
                int responseCode = response.getStatusLine().getStatusCode();
                if (responseCode == 302) {
                    Header locationHeader = response.getFirstHeader("Location");
                    location = locationHeader.getValue();
                }
            }catch(IOException e){
                e.printStackTrace();
            }catch (URISyntaxException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    httpclient.close();
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            System.out.println(location);
        }
    
        public static String encrypt( String str, String publicKey ) throws Exception{
            //base64编码的公钥
            byte[] decoded = Base64.decodeBase64(publicKey);
            RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
            //RSA加密
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
            return outStr;
        }
    }

2、直接获取302跳转后的页面内容，核心（HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();）

public static void main(String[] args) throws Exception {
            String json = "{\"Issuer_NAME\":\"MTDP\",\"EUID\":\"fccab33e-015e-11ea-95d9-000c292235b2\",\"Campaign_ID\":\"15814865334230070\"}";
            //String a = new String(encryptByPublicKey(json.getBytes(),publicKey));
            //String b = new String(decryptByPrivateKey(a.getBytes(),privateKey));
    
            System.out.println(json);
            CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
            HttpClientContext context = HttpClientContext.create();
    
            HttpPost httpPost = new HttpPost("https://vvans-uat.swiftpass.cn/vere/terminal/h5/home");
    
            CloseableHttpResponse response = null;
            String location = null;
            try {
                Map<String,String> map = new HashMap<>();
                map.put("data", encrypt(json,"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvhnuoppOFs/L+VmgRNjopZcP3Kz+7fF0UCag8aCc6jPU2+JUgg5su3McI2IP40aQeU9Z+KxFTuYZ1J8Ib35T+s8sbn2gv3rG+xdwSxVh81lKZ0fulZKox6WtHaDPykpJgkNsB9d1izg83OX0R3mwnLrh3XvGlFUQKsmrh92LfM9Kr/bFVzyNviaT1qoIBImIzSlbe/2tRo3rt5jRBU386E6iJq9KPSzwGwZ3Y3ZgTPgxXStxPuBbtcFQIEhZV2usv0ws7As1Az2tdpAfcAvVKRxsi2Dc/44DFUhtXjsqa7HU/GQKalXW9HbZUa2mTZH0+Ur8OBAiH/NrK/4Ndxfz3wIDAQAB"));
                //map.put("data","WEsUKl/ZYYBv6BwIuevduVc1XIB5WiVyhIryK5oy/UScOJ7ThODDJjFHeccFBPJDCNV4KMirACvZVFkYAqGuz3k71cA1AF+ZBbap+wjMRnNNd1GuwyVa1+fONxEPg/kY0jYCIuFK9sUJW5liMGbq+rNY+1J3dFYmHkscm3XYbJRC2kj6NZdpMh2VcOFoI5kHJaa0rWYX5uhpre7vr085B1XOjl8lGzvqtASl+kJwmMbEbo2Yvy0KaXoOkgzHaNrEVJsQaIiFPWv9gpP3KVXNFQDkONNThyCE2BkvJOfBB1SpZAoNzk2p7+WTT/rfUn86vrpFysn3oyzqWUfcA438IQ==");
                List<BasicNameValuePair> pair =new ArrayList<BasicNameValuePair>();
    
                //我们遍历map 将数据转化为我们的表单数据
                for (Map.Entry<String,String> entry:
                        map.entrySet()) {
                    pair.add(new BasicNameValuePair(entry.getKey(),entry.getValue()));
                }
    
                //httppost 中放入我们的经过url编码的表单参数
    
                httpPost.setEntity(new UrlEncodedFormEntity(pair));
                response = httpclient.execute(httpPost, context);
                int responseCode = response.getStatusLine().getStatusCode();
    
                System.out.println(EntityUtils.toString(response.getEntity()));
               
            }catch(IOException e){
                e.printStackTrace();
            }catch (URISyntaxException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    httpclient.close();
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            System.out.println(location);
        }

具体来看一下 LaxRedirectStrategy 的 redirect策略内部是怎么实现的？

可以看到继承了DefaultRedirectStrategy类，且初始化了 get，post，head和delete方法

@Contract(threading = ThreadingBehavior.IMMUTABLE)
    public class LaxRedirectStrategy extends DefaultRedirectStrategy {
    
        public static final LaxRedirectStrategy INSTANCE = new LaxRedirectStrategy();
    
        public LaxRedirectStrategy() {
            super(new String[] {
                HttpGet.METHOD_NAME,
                HttpPost.METHOD_NAME,
                HttpHead.METHOD_NAME,
                HttpDelete.METHOD_NAME
            });
        }
    
    }

继续看DefaultRedirectStrategy的核心方法，redirectMethods就是初始化时的String\[\] 数组，里面有get、post、head、delete方法

@Override
        public boolean isRedirected(
                final HttpRequest request,
                final HttpResponse response,
                final HttpContext context) throws ProtocolException {
            Args.notNull(request, "HTTP request");
            Args.notNull(response, "HTTP response");
    
            final int statusCode = response.getStatusLine().getStatusCode();
            final String method = request.getRequestLine().getMethod();
            final Header locationHeader = response.getFirstHeader("location");
            switch (statusCode) {
            case HttpStatus.SC_MOVED_TEMPORARILY: //302
                return isRedirectable(method) && locationHeader != null;
            case HttpStatus.SC_MOVED_PERMANENTLY: //301
            case HttpStatus.SC_TEMPORARY_REDIRECT: //307
                return isRedirectable(method);
            case HttpStatus.SC_SEE_OTHER:
                return true;
            default:
                return false;
            } //end of switch
        }
    
    
        protected boolean isRedirectable(final String method) {
            return Arrays.binarySearch(redirectMethods, method) >= 0;
        }

综上可以知道，isRedirected方法返回true，则请求在遇到302后会继续请求，访问最后的跳转地址并获取内容。

于此同事可以看到，默认的redirect策略选项是 DefaultRedirectStrategy

public DefaultRedirectStrategy() {
            this(new String[] {
                HttpGet.METHOD_NAME,
                HttpHead.METHOD_NAME
            });
        }

可以看到，默认情况下，只对get和head方法生效，和上面探讨的get模式中默认值是一致的，都是继续请求获取302后的内容。